The microemulsions, with a chemical composition similar to that of the LDL (low density, lipoprotein) and without protein, can join the LDL specific receptors, which exist in most tissues of the body. These microemulsions have a hydrophobic nucleus, consisting of cholesterol esters, though it can also present triglycerides and, surrounding the nucleus, there is a monolayer of phospholipides, though free cholesterol can also be found. The microemulsions are prepared by exposing to ultrasound the lipids that form these microemulsions, in an aqueous medium, and can be purified by various methods, such as ultracentrifugation or gel filtration. The lipidic mixture can also be emulsified by passing through the press of French. The microemulsions, when ejected in the blood stream, incorporate to their surfaces the apolipoprotein E (apo R), which exists in the plasma, associated to the plasmatic lipoproteins or in the free form. Thus, the apolipoprotein E serves as a linking element between the particles of the microemulsion and the LDL receptors, which recognize the apo E. It is known in the literature that the LDL receptors are highly increased in several lineages of neoplastic cells. Anticancer drugs can be incorporated to the LDL, reaching high concentrations in the neoplastic cells that have an increased expression of the receptors, and avoiding the normal cells, whose LDL receptors are comparatively reduced. It is therefore possible to send drugs specifically to the endoplastic tissues, avoiding the toxic effects of these drugs on the normal tissues and organs. The plasmatic LDL are not feasible for the treatment, due to technical reasons. Nevertheless, the artificially produced microemulsions can substitute the plasmatic LDL as carriers for chemotherapeutic agents, since they can also join the LDL receptors, though by means of another protein, the apo E, whereas the LDL joins the receptors by means of the apo D. This hypothesis has been confirmed in patients with acute myeloid leukemia (AML), a disease in which the LDL receptors are 3 to 100 times increased. In this group, the plasmatic removal of the microemulsions, marked with a radioactive cholesterol ester, was much faster than when ejected in normal individuals, or in individuals with acute lymphocytic leukemia, a disease in which the expression of the receptors is normal. When the AML patients were treated, achieving the remission of the disease, a condition in which the cells with exceeding LDL receptors disappear, the plasmatic removal of the microemulsions normalized, clearly showing that the microemulsions have the capacity of specific penetration into the neoplastic cells. Anticancer drugs, mainly those of hydrophobic nature, can thus be incorporated to the microemulsions, which conduct said drugs to the cancerous cells, minimally affecting the normal tissues, thereby highly reducing the toxic aggression of the chemotherapeutlc agent. This occurs whenever the cancer lineage has an increased expression of the LDL receptors, as already described in the literature relative to acute myeloid leukemia, myeloproliferous diseases, glioma, endometrial carcinoma, carcinoma of the prostate, uterine carcinoma, cancer of the breast, cancer of the gall bladder and cancer of the lung. Due to their high affinity for the receptors, the microemulsions marked with radioactivity or other means, can also be useful for diagnostical purposes or for localizing malignant tumors. The microemulsions marked, for example, with 99 m Tc-perteclmtate radioisotopes, were capable of generating nuclear medicine images of solid tumors, such as mammary carcinoma, carcinoma of the gall bladder, etc.